LONDON, Jan 22 (Reuters) - People with schizophrenia have genetic mutations that cluster in specific proteins key to the workings of the brain, according to research that suggests a fresh way to look at the illness and links it to other brain disorders such as autism.

In two research papers published in the Journal Nature, which together made up the largest genetic study of its kind, scientists analysed new or "de novo" gene mutations in people with schizophrenia and found they tend to disrupt sets of proteins which have related functions in the brain.

"De novo" gene mutations are found in affected people but not in their parents - in other words they are not inherited.

As well as identifying how genetic mutations affect brain function, findings also point to an overlap with the causes of other brain disorders such as autism and intellectual disability, the researchers said.

"The fact we've been able to identify a degree of overlap between the underlying causes of schizophrenia and those in autism and intellectual disability suggest...these disorders might share some common mechanisms," said Mick O'Donovan of Britain's Cardiff University, who jointly led the research.

He said the combined finding "tells us that for the first time we have a handle on one of the core brain processes that (are) disrupted in the disorder".

Schizophrenia is one of the most common serious psychiatric illnesses, affecting around 1 in 100 people worldwide. Scientists are not clear exactly what causes it, but believe it could be a combination of a genetic predisposition to the condition as well as environmental factors.

Working with teams from the Icahn School of Medicine at Mount Sinai, New York, the Broad Institute of the Massachusetts Institute of Technology, from Harvard and from Britain's Cambridge University, researchers examined DNA blood samples from 623 schizophrenia patients and their parents.

In a separate study, a second team analysed gene sequences of more than 2,500 people with schizophrenia and around the same number of controls as a comparison.

Their teams found that de novo mutations play a role in triggering schizophrenia, and also that they appear clustered in proteins that are involved in modulating the strength of connections between nerve cells and that play important roles in brain development, learning, memory and cognition.

The Broad Institute's Shaun Purcell, who worked on both studies, said the result was "sobering but also revealing".

"Despite the considerable sample sizes, no individual gene could be unambiguously implicated in either study," he said.

"It suggests that many genes underlie risk for schizophrenia and so any two patients are unlikely to share the same profile of risk genes." (Reporting by Kate Kelland, editing by Mark Heinrich)